1. Field of the Invention
The present invention relates to an image sensing apparatus using a charge-coupled device of a frame interline-transfer system (hereinafter referred to as an "FIT-CCD"), and more specifically to an image sensing apparatus capable of greatly reducing smears which occur in the FIT-CCD.
2. Description of the Related Art
There has heretofore been proposed a pseudo-frame imaging technique employed in an electronic still camera of a type wherein an FIT-CCD is used and its driving method is changed to photographically record a still picture.
In the above pseudo-frame imaging technique, however, signal charges of B fields should be allowed to remain in corresponding vertical charge transfer paths for about 1 V period (16.6 msec). Therefore, smears are produced so as to increase the electric charges of the B fields. As a result, there are produced differences in signal level between A and B fields, thereby producing so-called field flicker.
In order to reduce the field flicker, there have been proposed electrically-correcting methods such as a method of carrying out a gain modulation process for each field, a method of controlling exposure time of each of the A and B fields, etc. However, these correcting methods should be controlled for each shutter speed. Therefore, a systematic technique for controlling each of the correcting methods is complicated and sufficient space for disposing a correction circuit is required, thereby encountering difficulties in accommodating the correction circuit in the electronic still camera which has been under demand for the reduction in size.